1. Field of the Invention
This invention relates to fatliquoring agents which may be used simultaneously with electrolyte tanning liquors in leather manufacture.
2. Statment of the Related Art
Generally, the process steps in the manufacture of leather from hides which have already been fleshed, unhaired, bated, and pickled, comprise sequentially: tanning (to convert the hide into a stable, non-putrescible material, usually using chromium or aluminum salts); wringing (to remove excess moisture); splitting and shaving/skiving (to adjust the thickness); retanning (to impart desirable properties of other tanning agents); coloring or tinting (where desired); fatliquoring (to lubricate the fibers for flexibility); followed by various non-chemical steps such as conditioning, staking, buffing, finishing, and plating. The existence of so many steps results in a labor-intensive and/or machinery-intensive manufacturing process with resultant high costs. Therefore, anything which will combine steps or reduce or eliminate a step is of great economic importance, in addition to any improved properties of the leather that may result. Furthermore, it would be useful if a fat-liquoring composition could be at least partially combined with the tanning and/or retanning compositions. This would increase leather suppleness and grain stability, and also would make the fatliquor composition more versatile, since it would not be necessary to remove the tanning liquor when fatliquoring.
Published German patent application No. 16 69 347 describes a process for the fatliquoring of leather using water-emulsifiable sulfosuccinic acid esters which have been obtained by the esterification of fat- or oil-like compounds containing alcoholic hydroxyl groups and also lipophilic residues with maleic acid anhydride followed by reaction of the esterification product with a sulfite or bisulfite in a quantity substantially equimolar to the maleic acid anhydride used. However, the use of compounds such as these is confined to fatliquoring. They cannot be used during chrome or aluminum tanning or retanning on account of the inadequate emulsion stability of the sulfosuccinic acid esters with respect to chromium or aluminum salts, and therefore cannot afford the advantages of the present invention.